Projetos de Engenharia Mecânica

Division of the resulting forces in biomechanics platforms

This study has had as finality to evaluate the possibility of the utilization of a measurement system of the pressure distribution to determine the components of the resulting force, correspondent to each partial loading, when a double loading occurs on the biomechanics platforms.

• Texto completo - Full text



• Ambulatory assessment of 3D ground reaction force using plantar pressure distribution
H. Rouhani, J. Favre, X. Crevoisier, K. Aminian
"This study aimed to use the plantar pressure insole for estimating the three-dimensional ground reaction force (GRF) as well as the frictional torque (TF) during walking. The result obtained for the patients showed higher error; nevertheless, when the data of the same patient were used for learning, the results were improved and in general slight differences with healthy subjects were observed. In conclusion, this study showed that ambulatory pressure insole with data normalization, an optimal choice of inputs and a well-trained nonlinear mapping function can estimate efficiently the three-dimensional ground reaction force and frictional torque in consecutive gait cycle without requiring a force-plate."

Method to estimate the localization of the thigh frontal plane
to apply in Gait Analysis

The objective of this study were to determine an additional method to estimate the thigh frontal plane, where afterwards will be generated a local coordinates system for a measurement of the relatives movements between the thigh and its adjacent segments: pelvis and shank. The measured values of the hip rotation and valgus-varus of the knee, by a gait analysis system, suffer important changes due to the error in the frontal plane of the thigh determination, what may affect negatively the clinical decision to be followed.

The estimation of the thigh frontal plane was performed through of the determination of a control variable related to the rotations occurred on the knee joint, to a determined type of movement performed, as described in the section 2.3. The knee flexion-extension axis and, by consequence, the thigh frontal plane, derive from this control variable.

The validity of utilization of this method was verified by mean of a realization and later statistics comparison from a series of 23 exams of gait in normal subjects, where were used the value generated by the control variable and by the standard protocol of gait analysis, with the use of the Knee Alignment Device (KAD).

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Engenharia Reversa com Sistemas de MoCap - Reverse Engineering

É possível utilizar um sistema óptico de captura de movimento 3D para realizar engenharia reversa (escaneamento) de superfícies rígidas. O sólido para escaneamento deve ter uma posição invariável no sistema de coordenadas global do laboratório, ou ter um 'cluster' de 3 ou 4 marcadores fixado em algum ponto de sua superfície. Um apontador (pointer) é então deslocado sobre a superfície do sólido. Programas CAD, de geração de malhas 3D, são empregados posteriormente para processar o arquivo de coordenadas do escaneamento.

• Exemplo: nuvem de pontos 3D
Crânio de resina escaneado em um sistema de captura de movimento Vicon 370
Frequência de aquisição 60Hz

O impacto das medidas da torção tibial feita por meio de goniometria e
cinemática tridimensional nos resultados da análise de marcha (rascunho)

The impact of the measures of tibial torsion made by goniometry and
three-dimensional kinematics in the results of gait analysis (draft)

Rascunho 1: A medição da torção tibial (TT), embora importante para a elaboração de planejamentos de reabilitação [x] e para a estruturação de modelos biomecâncios precisos, tem se mostrado dificil como parte dos procedimentos empregados na análise clínica de marcha (ACM) [x]. Os métodos para medição da TT podem ser divididos em dois grupos: clínico e cinemático. O presente estudo fez uso dos dois métodos para avaliar a correlação estatística entre ambos e, posteriormente, mensurar a propagação de seus resultados na cinemática e cinética do joelho e tornozelo determinados pela ACM.

O método clínico [Staheli et al.,1985] fez uso de um goniômetro e uma maca, que serviu como plano transvesal de referência, e teve o paciente posicionado em decúbito ventral com o joelho flexionado até que a tíbia se encontrasse perpendicular ao plano de referência. Uma das hastes do goniômetro foi alinhada ao eixo transmaleolar, apoiado à planta do pé, corrigida para estar pararlela ao plano de referência. A outra haste foi alinhada ao eixo axial do femur, que interliga a cabeça do femur ao centro articular do joelho – ponto médio entre os epicôndilos.

Este método é de dificil execução e reprodutibilidade [x], pois alguns ligamentos do joelho estão sob tensão mínima [x], o que permite movimento de rotação axial da tíbia, e consequente alteração na medição da TT, e todos os pontos de referência do femur são internos, o que exige uma estimativa visual na medição goniométrica.

O método cinemático foi baseado no princípio [x] de que a correta orientação do eixo do joelho, e do plano frontal da coxa, implica na minimização da amplitude da onda de valgo-varo na fase de balanço do ciclo de marcha. Assim, após um trial dinâmico, o eixo do joelho foi orientado para obter este resultado com auxílio de um ‘knee alignment device’ (KAD) [x]. Um trial estático complementar foi realizado, com marcadores adicionais posicionados sobre os maléolos mediais internos para a determinação do eixo do tornozelo, e a torção tibial foi calculada com a projeção do eixo do joelho no plano tranverso da tíbia.

As fontes de erro deste processo estão relacionadas à falhas de posicionamento de marcadores e do KAD, a subjectividade na avaliação da adequada variação da amplitude da onda de valgo-varo do joelho e a interferência da rotação axial dos joelhos em pacientes com postura agachada durante o trial estático complementar.

Translation

Draft 1: Although the measurement of tibial torsion (TT) is important for the development of rehabilitation plans [x] and for structuring precise biomechanical models, it has been proven to be difficult as part of the procedures used in clinical gait analysis (MCA) [x]. The methods for measuring TT may be divided into two groups: clinical and kinematic. In this study two methods are used to evaluate the statistical correlation between those methods and, later, measure the spread of their results on kinetics and kinematics of the knee and the ankle, as determined by the ACM.

The clinical method [Staheli et al., 1985] used a goniometer and a stretcher, which worked as transvese reference plan. The patient was in prone position with the knee bended so that the tibia was found perpendicular to the reference plan. One of the goniometer stems was aligned with the transmalleolar axis leaning on the arch and realigned so that it stood paralel to the plan. The other rod was aligned with the axial length of the femur, which connects the head of the femur to the knee joint center - the midpoint between the epicondyles.

This method is difficult to perform and reproduce [x] because some knee ligaments are under minimal tension [x], which allows axial rotation of the tibia, changing the results of TT measurement and requiring a visual estimate in goniometric measurement.

The kinematic method was based on the principle [x] that the correct orientation of the axis of the knee and of the frontal plane of the thigh implies the minimization of the amplitude of the valgus-varus wave in the swing phase of gait cycle. So, after a dynamic trial the axis of the knee was orientated to achieve this result with the aid of a knee alignment device (KAD) [x]. An additional static trial was conducted with additional markers placed over the medial malleolus for determining the internal axis of the ankle, and tibial torsion was calculated with the projection of the axis of the knee in the transverse plane of the tibia.

The sources of error in this process are related to:
- Failures while of markers and KAD;
- Subjectivity in assessing the appropriate amplitude variation of the knee valgus-varus wave;
- Interference of the axial rotation of the knee in patients squatting position during the complementary static trial.

• BodyBuilder code (Vicon Motion Systems Ltd) / Static c3d file
BodyBuilder code for calculating tibial torsion with the addition of markers in the medial malleoli (L/Rank2) and sample file (Trial03.c3d).
Note: Use the Mokka application to view the stickfigure and MS Notepad for *.mod files.

Paper: Acta Ortopédica Brasileira

• The impact of tibial torsion measurements on gait analysis kinematics - (open access)
DOI: http://dx.doi.org/10.1590/1413-78522014220500579

"Objective: To measure and compare tibial torsion values as assessed by goniometry and three-dimensional kinematics. In addition, the impact of each one of these measurements on kinematic and kinetic results for normal gait was determined.
Conclusion: Although statistical correlation among tibial torsion angles by goniometry and three-dimensional kinematic were moderate, kinematic and kinetic analysis of the joints did not reveal any significant changes. Level of Evidence I, Diagnostic Studies - Investigating a Diagnostic Test."

Device project: Gait training with partial weight bearing

Draft 1: Normal Gait

Draft 2: Ankle dorsiflexion blocked (AFO simulation)

Treadmill velocity calculation:
calculation of variations in belt speed due to dynamic loading

Some treadmill running exams consistently showed variation in belt speed. In video I (Treadmill motion analysis) the speed graph shows a peak in the double swing phase - the belt speed is decreased under dynamic loads. Perhaps only a few classes of equipment have variations in speed. Additional studies would be needed to verify this hypothesis.

A draft calculation, with the generation of a local coordinate system on the treadmill, was developed with a set of three reflective 2d markers attached to the belt treadmill. Videos II (Gait Analysis on the Treadmill: Global Coordinate System) and III (Gait Analysis on the Treadmill: Local Coordinate System), with a brief description, are available below. Routines in the BodyBuilder programming language and c3d files (pre- and post-processing) are attached in file below: trial_04_hiae_3.zip (1).

The calculation model was divided into 3 routines (2) due to some processing failures - perhaps the programming can be redone and improved, whether in BodyBuilder or Matlab and Python.

(1) c3d files and speed graphics can be viewed in the Mokka application.
(2) software used to motion capture and process routines: Vicon Nexus 1.5.1 and BodyBuilder 3.6.4 respectively.

Processing sequence:
a - BodyBuilder macro: "5e_field offset.mod" / save c3d
b - BodyBuilder macro: "esteira - 5f_fieldoffset.mod" / close c3d file
c - In Nexus 1.5.1 apply Woltring filter (the markers P1, P2 and P3 were excluded by previous processing of the "Fill Gaps" command)
d - BodyBuilder macro: "esteira-mkr_gait - 5g_field offset.mod"
note: *.mp files can be read and edited on MS Windows Notepad.

Note: BodyBuilder function
BODYBUILDER FOR BIOMECHANICS: Special Functions (page: 116)
<<
[ ] is a special "field offset" post-fix function used to find the final value of an expression in any field, relative to the current one.
segment P[-1] segment P in previous field
The "sample offset" function has many uses, including the creation of special filters.
>>

Video I: Treadmill motion analysis

Video II:
Gait Analysis on the Treadmill: Global Coordinate System (GCS)

Video III:
Gait Analysis on the Treadmill: Local Coordinate System (LCS)

• BodyBuilder code (Vicon Motion Systems Ltd) and dinamic c3d files: (1) trial_04_hiae_3.zip




Notes:

I apologize for the simplified explanation and the translation flaws.
All criticisms about the mathematical model or programming logic will be useful.